1. FIELD OF THE INVENTION
The present invention generally relates to a long span truss of substantially conventional steel construction provided with concrete encasement of the top and bottom chords with the concrete encasement being reinforced and the concrete encasement on the bottom chord and optionally on the top chord including post-tensioned steel tendons. The invention further relates to a method of making the truss as described above in which the light structural steel truss is first erected and provided with temporary steel scaffolding and bracing to support formwork. Reinforcing steel and steel tendons are placed in the formwork and concrete is poured to encase the top and bottom chords of the truss. The steel tendons are post-tensioned to provide maximum load support capability. The truss of the present invention can be used in situation where trusses are used to carry heavy loads over long spans such as bridges, stadiums, convention halls and the like and is especially beneficial when spanning a busy highway or waterway with the trusses including a single span or continuous trusses of two or more spans in which one or more intermediate supports are employed.
2. DESCRIPTION OF THE PRIOR ART
Trusses of various configurations and arrangements have been utilized in structures and usually include a top chord and a bottom chord interconnected by vertical and diagonal brace members rigidly connected together with the ends of the truss being supported which introduces tension forces to the bottom chord and compression forces to the top chord. In other instances, a continuous truss is supported at intermediate points as well as at the ends thus introducing tension forces to the top chord as well a the bottom chord depending upon the relationship between the truss and the support points. It is well known to encase or clad components of the truss in concrete for increasing the strength of the truss, insulation, fireproofing and other well known purposes. Prior truss structures do not include the concept of encasing the top and bottom chords in concrete after the truss has been erected with the truss being constructed of relatively lightweight steel which supports formwork to pour the concrete to encase the top and bottom chords of the truss with the bottom chord and optionally the top chord including steel tendons that are post-tensioned to obtain maximum load supporting characteristics for the truss.